An optimal and a heuristic approach to solve the route and spectrum allocation problem in OFDM networks

To maximize the usage of optical resources, it is important to reduce the total bandwidth requirement for communication. Orthogonal Frequency Division Multiplexing (OFDM) has recently emerged as an encouraging competitor to Wavelength Division Multiplexing (WDM), which uses fixed capacity channels. A network using OFDM-based Spectrum-sliced Elastic Optical Path (SLICE) has a higher spectrum efficiency, due to the fine granularity of subcarrier frequencies used. To minimize the utilized spectrum in SLICE networks, the routing and spectrum allocation problem (RSA) has to be efficiently solved. We have solved the RSA problem using two Integer Linear Programming (ILP) formulations. Our first formulation provides an optimal solution, based on an exhaustive search and is useful as a benchmark. Our second approach reduces the time requirement by restricting the number of paths considered for each commodity, without significantly compromising on the solution quality. We have compared our approaches with another prominent formulation proposed recently

Security Analysis of the Evolved Packet Core for LTE Networks

Originally cellular networks handled calls and short messages only. Today, this has been extended to handle packet data services. However now the world is moving towards an entirely IP based mobile service based on LTE and the Evolved Packet Core. Security becomes even more important than before. Cellular networks will be using the same technology that runs the Internet, which could leave them open to a range of threats from the air interface side of the network, especially with the popularity of smart phones and USB "Mobile Broadband" modems. This thesis investigated a range of network protocols used in the Evolved Packet Core, as well as the possibility of attacks against these networks and their protocols and whether such attacks can be achieved, especially from cheap handheld devices. Further this thesis presents results showing that these network protocols are free from serious flaws in their specification

EPro-PnP: Generalized End-to-End Probabilistic Perspective-n-Points for Monocular Object Pose Estimation

Locating 3D objects from a single RGB image via Perspective-n-Points (PnP) is a long-standing problem in computer vision. Driven by end-to-end deep learning, recent studies suggest interpreting PnP as a differentiable layer, so that 2D-3D point correspondences can be partly learned by backpropagating the gradient w.r.t. object pose. Yet, learning the entire set of unrestricted 2D-3D points from scratch fails to converge with existing approaches, since the deterministic pose is inherently non-differentiable. In this paper, we propose the EPro-PnP, a probabilistic PnP layer for general end-to-end pose estimation, which outputs a distribution of pose on the SE(3) manifold, essentially bringing categorical Softmax to the continuous domain. The 2D-3D coordinates and corresponding weights are treated as intermediate variables learned by minimizing the KL divergence between the predicted and target pose distribution. The underlying principle unifies the existing approaches and resembles the attention mechanism. EPro-PnP significantly outperforms competitive baselines, closing the gap between PnP-based method and the task-specific leaders on the LineMOD 6DoF pose estimation and nuScenes 3D object detection benchmarks.Comment: CVPR 2022 Oral, code available at https://github.com/tjiiv-cprg/EPro-PnP. V3 notes: correct Fig 8 and a few expression

Analysis and evaluation of harmonic distortion in industrial networks caused by HVAC air-conditioning systems

The topic of this research, conducted at Mitsubishi Electric Hydronics, in the form of an internship, it is the development of a simulation program for the calculation of the harmonic distortion of conditioning machines. The environment in which the simulation program will be implemented is the Neplan software. Well'study the machines in use and their electrical characteristics, focusing on the harmonic distortion that these generate when they are connected to the proprietary network.ope

Development and Fabrication of Thermally Conductive Polymer Matrix Composite Foams

Advancements in the electronics industry have led to miniaturized components with increased computing power, which resulted in serious heat management issue. Under such technological trend, the development of new multifunctional packaging materials with excellent thermal conductivity and electrical resistivity, which can be used for heat dissipation, is becoming increasingly important. A recent research revealed the possibility of using foaming-induced filler alignment to promote the effective thermal conductivity (keff). In this context, this thesis research aims to develop thermally conductive polymer matrix composite (PMC) foams that can provide a solution to the heat management of new electronic devices. First, an analytical model was constructed to confirm the feasibility of foaming-induced keff enhancement. This model considered filler alignment caused by foaming-induced stress field, and calculated the keff using the concept of thermal resistor network. Second, a comprehensive experimental study was conducted to parametrically reveal the dependency of PMCs keff on foam morphological parameters, including filler size, foam expansion ratio, cell size, and cell population density. Low density polyethylene (LDPE)-hexagonal boron nitride (hBN) composites blown by Expancel microspheres were studied as a case example to prove the concept

CONSENSUS, PREDICTION AND OPTIMIZATION IN DIRECTED NETWORKS

This dissertation develops theory and algorithms for distributed consensus in multi-agent networks. The models considered are opinion dynamics models based on the well known DeGroot model. We study the following three related topics: consensus of networks with leaders, consensus prediction, and distributed optimization. First, we revisit the problem of agreement seeking in a weighted directed network in the presence of leaders. We develop new sufficient conditions that are weaker than existing conditions for guaranteeing consensus for both fixed and switching network topologies, emphasizing the importance not only of persistent connectivity between the leader and the followers but also of the strength of the connections. We then study the problem of a leader aiming to maximize its influence on the opinions of the network agents through targeted connection with a limited number of agents, possibly in the presence of another leader having a competing opinion. We reveal fundamental properties of leader influence defined in terms of either the transient behavior or the achieved steady state opinions of the network agents. In particular, not only is the degree of this influence a supermodular set function, but its continuous relaxation is also convex for any strongly connected directed network. These results pave the way for developing efficient approximation algorithms admitting certain quality certifications, which when combined can provide effective tools and better analysis for optimal influence spreading in large networks. Second, we introduce and investigate problems of network monitoring and consensus prediction. Here, an observer, without exact knowledge of the network, seeks to determine in the shortest possible time the asymptotic agreement value by monitoring a subset of the agents. We uncover a fundamental limit on the minimum required monitoring time for the case of a single observed node, and analyze the case of multiple observed nodes. We provide conditions for achieving the limit in the former case and develop algorithms toward achieving conjectured bounds in the latter through local observation and local computation. Third, we study a distributed optimization problem where a network of agents seeks to minimize the sum of the agents' individual objective functions while each agent may be associated with a separate local constraint. We develop new distributed algorithms for solving this problem. In these algorithms, consensus prediction is employed as a means to achieve fast convergence rates, possibly in finite time. An advantage of our distributed optimization algorithms is that they work under milder assumptions on the network weight matrix than are commonly assumed in the literature. Most distributed algorithms require undirected networks. Consensus-based algorithms can apply to directed networks under an assumption that the network weight matrix is doubly stochastic (i.e., both row stochastic and column stochastic), or in some recent literature only column stochastic. Our algorithms work for directed networks and only require row stochasticity, a mild assumption. Doubly stochastic or column stochastic weight matrices can be hard to arrange locally, especially in broadcast-based communication. We achieve the simplification to the row stochastic assumption through a distributed rescaling technique. Next, we develop a unified convergence analysis of a distributed projected subgradient algorithm and its variation that can be applied to both unconstrained and constrained problems without assuming boundedness or commonality of the local constraint sets

Fatigue Enhancement of Undersized, Drilled Crack-Arrest Holes

Fatigue cracks occur in steel bridges from repeated loads. If allowed to continue to grow, eventually the fatigue cracks will require either expensive repairs or reduction of traffic loads on the bridge, or they may lead to the failure of the bridge. The objective of this research was to develop a new, cost-effective technique that can be used to arrest the growth of fatigue cracks before they develop to an extent that more expensive repairs are required. It is well known that drilling a hole (crack-stop hole) at each end of a fatigue crack can arrest the growth of the fatigue crack. This new technique consisted of cold-expanding a crack-arrest hole thereby cold-working the material around the hole and subjecting the cold-worked material to ultrasonic vibration. It was hypothesized that this process would increase fatigue crack initiation life three ways. First, the compressive force used to cold-expand the hole would result in residual compressive stress fields around the hole when the radial force was removed. Second, the cold-expansion would cause strain-hardening and cold-working with a concomitant increase in the yield and ultimate strengths of the steel. Third, the ultrasonic vibration from the PICK treatment would further increase the resistance to fatigue propagation by increasing the yield and ultimate strengths and increasing the radial extent of the residual compressive stress field. These expected results and their effects on fatigue crack initiation were investigated through a proof-of-concept testing program using reduced-scale, laboratory models and by mathematical modeling

NSCL na plataforma ETSI M2M

Mestrado em Engenharia de Computadores e TelemáticaThe evolution of every day gadgets into smart-devices able to react to their surrounding environment is enabling the development of novel applications aiming revolutionize the industry related to this technology. Currently much attention has been given to standardizing IoT and M2M in order to build an interoperable foundation that will enable the growth of the future Internet, where devices will communicate without, or at least minimizing, human intervention. In this dissertation is presented in first place issues such as: heterogeneity, scalability, addressing and the first approach taken by the ETSI M2M standard. Subsequently, is presented the ETSI M2M vision and high-level architecture together with current work in this area. Finally an implementation of the network middleware is going to be presented along with further testing.A evolução dos dispositivos do dia a dia em dispositivos inteligentes capazes de reagir ao ambiente que os rodeia está a permitir a criação de novas aplicações que visam revolucionar a industria. Atualmente tem-se dado muita atenção a estandardização da Internet das Coisas e comunicações máquinaa- máquina, com o objetivo de construir uma fundação interoperável que permitirá o crescimento futuro da Internet, onde os dispositivos irão comunicar sem, ou com mínima, intervenção humana. Nesta dissertação é apresentado em primeiro lugar requisitos como heterogeneidade, escalabilidade, endereçamento e a primeira abordagem feita pelo standard M2M do ETSI. Consequentemente, é a apresentada a visão e a arquitetura e o trabalho realizado nesta área. Por fim é apresentada a implementação da componente de rede realizada nesta dissertação juntamente com os respetivos testes